Vehicular theft constitutes a high percentage of reported criminal acts. Yet, because of the number of vehicles traveling the highways, the identification of stolen vehicles is practically impossible. If the stolen vehicle is driven across the national border, the chance of recovery is virtually non-existent. Some vehicles are even stolen from attended garages and parking lots and thieves' ingenuity has overcome the most complex and safest mechanical locking devices.
It has been proposed in the past to conceal on board vehicles radio frequency transmitters which would be triggered into operation by the motion of the vehicle. Directional radio finders could then be used to locate the vehicle once its theft has been reported to the authority. To be practical, such devices should be powerful enough to transmit over a range of several miles and for a period of time spanning several days. The size of the batteries required to power such transmitter and of other components would interfere with their easy concealment on the monitored equipment.
Kidnapping for ransom or for political motives is almost a daily occurrence throughout the world. Most countermeasures against this type of criminal activity have been mostly preventive. Once a person has been kidnapped, means are seldom available to determine his whereabouts. A kidnap victim may even be walked out of his residence or place of work under the threat of a concealed weapon under the unsuspecting eyes of relatives, co-workers or security guards.
There is, therefore, a need for a signalling device small enough to be concealed within an object, in the lining of a piece of clothing or even under the skin of a potential kidnap victim and which would transmit a distress signal unbeknown to the crime perpetrator.